Park Tool DCA-1

Standard caliper jaws are often too thick to reach the actual braking surface of a disc rotor, meaning they measure the unworn outer edge instead. The DCA-1 uses protruding contact points to bypass that edge, giving you an accurate reading of how much material has actually worn away.

Yes, it is designed to be compatible with almost all standard vernier, dial, and digital calipers. It attaches securely to the jaws, allowing you to upgrade your existing tool without buying a specialized, expensive rotor gauge.

The DCA-1 features conical end points that seat perfectly into the bolt holes of your chainrings or cranks. Once seated, you simply measure the distance between the points using your calipers to calculate the BCD accurately.

Not at all. Because it attaches directly to your existing calipers, you simply zero out your caliper once the DCA-1 is installed. It is a straightforward, mechanical add-on that requires no complex calibration.

It is constructed from steel, making it robust enough for frequent use in a home workshop or a professional bike shop. It is a simple, single-piece tool with no moving parts to break or wear out.